Embodiments of the invention relate generally to electrical enclosures, and more particularly, to an apparatus and method of providing a locking mechanism for a cover to an electrical box that houses electronic equipment.
Enclosures for electrical equipment provide protection to the equipment from environmental conditions and prevent electrical shock to equipment users. The National Electrical Manufacturing Association (NEMA) publishes performance standards that different classes of electrical enclosures are to offer against environmental conditions and intrusion by foreign substances. NEMA standards specify construction requirements and testing criteria for enclosures and provide guidance on security of doors and covers to ensure the appropriate level of protection to electrical equipment and operators. An enclosure manufacturer will stipulate a NEMA rating and thereby claim a degree of protection for the enclosed electronic components against environmental hazards such as water, dust, icing, corrosives, acids, oil, and intrusion by people or animals.
Specific NEMA enclosure “Types” are specified for their appropriate applications and the environmental conditions against which they are designed to provide protection. For instance, basic NEMA enclosure applications for indoor nonhazardous use include protecting operators against accidental contact with enclosed equipment and preventing ingress of solid foreign objects such as falling dirt. Some NEMA enclosures provide further protection against ingress of dripping water and water from light splashing. Other NEMA enclosures are constructed for outdoor use and may be intended for applications in areas were rain, sleet, and the external formation of ice on the enclosure may be present. Still, other NEMA enclosures are constructed to protect against rain, hose-directed water, windblown dust, and more. To offer a degree of protection against tampering, some NEMA Types require a tool to gain access to the interior or require provisions for locking the enclosure.
FIGS. 1 and 2 show a prior art electrical enclosure 20 having an electrical box 22, an enclosure cover 24, and a locking provision to lock the enclosure cover 24 on the electrical box 22. The locking provision includes a front latch 26 on the enclosure cover 24 and a back latch 28 on the electrical box 22. The latches 26, 28 have a provision for a padlock and a provision for a lock rivet 30 to fasten the enclosure cover 24 to the electrical box 22. FIG. 3 shows a lock rivet 30 installed in a hole through the front latch 26 of the enclosure cover 24. The lock rivet 30 has a shaft 32 with a head 34 at one end and a hole through the shaft 32 at the other end through which a pin 36 is inserted. The lock rivet 30 is held in the front latch 26 permanently by the head 34 and pin 36. The back latch 28 of the electrical box 22 has an opening configured to receive the lock rivet 30 when the pin 36 is oriented in a certain direction and then retain it when the pin 36 is rotated to another direction.
With respect to the lock rivet 30, a machine riveting process is typically used to assemble the lock rivet 30 within the hole of the front latch 26. The machine riveting process requires an operator to load the enclosure cover 24 on the riveting machine, insert a pin 36 in an actuating arm of the machine, install a rivet through a hole in the front latch 26 of the enclosure cover 24, orient the rivet so that a hole in the rivet is positioned to receive the pin 36 from the machine, and then actuate the machine to drive the pin 36 into the rivet. Unfortunately, the machine riveting process leads to significant failure rates (e.g., 2 in every 10 parts) because jamming often destroys component parts during the machine actuation process. In addition, the machine riveting process leads to expenses in housing and operating the machine and in replacing failed parts. Also, the machine riveting process may pinch extremities or propel broken assembly parts at the operator at high speeds due to high compression forces of the machine.
It would therefore be desirable to design an apparatus and method to provide a locking mechanism for an electrical component enclosure that eliminates machine riveting and the associated failure rate, expense, and potential for injury.